JPS63240918A - Gas separating membrane - Google Patents

Abstract

PURPOSE:To obtain gas separating membrane having a separation factor balancing with a permeation velocity of O2 having also stable durability of performance by using a copolymer consisting of tetrafluoroethylene with vinylether contg. siloxane. CONSTITUTION:Thin film is formed from a copolymer consisting of tetrafluoroethylene and a vinylether contg. siloxane comprising vinyloxypropyl trimethyl siloxane such as 7,7,9,9-tetramethyl-3,8-dioxa-7,9-disiladecene-1, etc. Gas separating membrane is obtd. by superposing the thin film on porous film of polysulfone. Suitable proportion of each comonomer contained in the copolymer is generally 5-70mol.% tetrafluoroethylene and ca. 60-5mol.% vinylether contg. the siloxane. By copolymerizing if necessary, a specified third component such as alpha-olefin, etc. or further component, properties such as crosslinking property, adhesivity to a base material, etc. may be added to the copolymer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas separation membrane, in particular, a membrane separation method for separating acid from air.
When obtaining enriched air, the permeation amount of enriched air is large, and
This relates to a separation membrane with excellent oxygen permselectivity.

[Prior Art] Oxygen-enriched air with an oxygen concentration of 25 to 50% is required, for example, for blast furnace ventilation, combustion assistance, petroleum protein processing, waste liquid treatment, exhalation in medical care, and the like. The conventional method for obtaining oxygen-enriched air is to produce high-purity oxygen using cryogenic liquefaction distillation.

Then, air was mixed to obtain the desired oxygen concentration. However, in such a method, since the high purity acid [k] is generally contained in a pressure vessel, there are risks in handling the pressure vessel, or the necessity of a pressure regulator to keep the mixed gas concentration constant.
There were various problems such as the complexity of the operation.

On the other hand, as a method for obtaining 25-50% oxygen enriched air,
There is a membrane separation method.

This method directly provides oxygen-enriched air, is operationally simple, and is economically advantageous. As such a separation membrane, one in which a porous support is coated with amino- and Lζ-containing siloxane is known (Japanese Patent Laid-Open No. 59-1
(See Publication No. 20207).

The oxygen permeation rate of the Kono membrane is QO2 = 1.9X 10-:I
cm:'/ cm2sec cmHg (5,2m3/
m2. However, the oxygen/nitrogen separation coefficient (QO2/QN2) is as small as α=2.0, and there is a limit to the oxygen concentration of the oxygen-enriched air that can be obtained. On the other hand, fluorine-containing resins such as polyethylene terephthalate, polyethylene, polycarbonate, and tetrafluoroethylene-hexafluoropropylene copolymer have a large oxygen separation coefficient of 3 to 5, but an oxygen permeability coefficient of 1O-1°. ~
It cannot be expected to obtain oxygen-enriched air with a flow rate as small as loi1cm3cm/cm2sec c+aHg.

[Problems to be Solved by the Invention] In view of these points, the present invention has carried out various studies with the aim of obtaining a gas separation membrane that has a balance between the separation coefficient and the oxygen permeation rate, and whose performance can be maintained stably. , As a result of consideration,
It has been discovered that the above object can be achieved by forming a thin film of a previously unknown copolymer of tetrafluoroethylene and siloxane-containing vinyl ether and placing it on a polysulfone porous membrane.

[Means for Solving the Problems] Thus, the present invention provides a novel gas separation membrane in which a copolymer consisting of tetrafluoroethylene and siloxane-containing vinyl ether is made into a thin film and placed on a polysulfone porous membrane. be.

Examples of the siloxane-containing vinyl ether used in the present invention include: ? , 7,9.9-tetramethyl-3,
8-Dioxa-7,9-disiladecene-1,7,7-bis(trimethylsilyloxy)-8,9-dimethyl-3
, 8-dioxa-7,9-disiladecene-1 and other vinyloxypropyltrimethylsiloxysilane compounds.

Although the content ratio of each of these copolymers is strictly determined by the type of each compound used, it is generally appropriate to employ about 5 to 60 to 5 mol% of tetrafluoroethylene. Furthermore, if necessary, it is also possible to copolymerize a specific third or more component, which improves, for example, crosslinking properties,
Adhesion to the base material etc. can be imparted. Any other g introduced for such purpose. Examples of Hl> bodies include α-olefins, alkyl vinyl ethers, and vinyl esters.

If these content ratios deviate from the ranges listed in L, the separation coefficient and oxygen permeation rate will become insufficient, which is not preferable.

In fact, the means for producing the copolymer according to the present invention is not particularly limited, but includes, for example, solution polymerization carried out in an organic solvent using a radical initiator, and/or bulk polymerization without using a polymerization medium. Suspension polymerization and emulsion polymerization using water as a medium can also be employed. In addition, polymerization by radiation or plasma is also possible.

Further, it is appropriate that the homogeneous molecule 11 of the copolymer according to the present invention has an intrinsic viscosity [η] of 0.1 or more, preferably 0.2 or more.

The copolymer thus obtained is soluble at room temperature in, for example, fluorine-based solvents such as trichlorotrifluoroethane, and hydrocarbon-based solvents such as n-hexane, cyclohexane, and tetrahydrofuran. As a result, the present copolymer can be formed into a thin film of several liters or less on a support. There are no particular limitations on the means for forming such a thin film, and any known means may be employed as appropriate. The copolymer is dissolved in a solvent and porous ++5!
11-, and then evaporating the solvent, or by casting a thin film into a thin film and disposing it on a porous membrane.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.
It goes without saying that the present invention is not limited in any way by this explanation.

Example 1 Tetrafluoroethylene/siloxane-containing = nyl ether copolymer [tetrafluoroethylene/7,7,9.9
-tetramethyl-3,8-dioxa-7,9-disiladecene-l/hydroxybutyl vinyl ether composition ratio (molar ratio) 50/48.5/1.5, intrinsic viscosity [η]
= 0.75] in n-hexane (30 g/fL), and a polysulfone porous hollow fiber (outer diameter 450μ: inner ff 320μ;
An air permeation rate of 30 m3/rs2 hr atm) was passed through and coated on top. After the solvent was evaporated, 20 of them were bundled, one end was hardened with epoxy resin, and the other end was sealed to make a simple module with an effective length of 30 cm, and the gas permeability was measured for oxygen and nitrogen. Oxygen permeation rate is QO
2J, 28 m3/m2hr atm, oxygen/nitrogen separation factor was α=2.46.

Example 2 Tetrafluoroethylene/siloxane-containing vinyl ether copolymer [tetrafluoroethylene/7,7-bis(
trimethylsilyloxy)-9,S-dimethyl-3,8
-Dioxa-7,9-disiladecene-1/hydroxybutyl vinyl ether composition ratio (mole ratio) 50/48.5/
1.5, a solution of dolchlorotrifluoroethane (40 g/jl) with an intrinsic viscosity [η] = 0.231 was prepared, and a polysulfone porous hollow fiber (
Outer diameter 450μ; Inner diameter 320μ: Air permeation rate 30m3
/ m2 hr atm) and coated on top. After the solvent was evaporated, 20 of them were bundled, one end was hardened with epoxy resin, and the other end was sealed to make a simple module with an effective length of 30 crrr, and the gas permeability was determined as 4111 for oxygen and nitrogen. Oxygen permeation rate is QO2J, 50m3
/ m2hr atm, oxygen/nitrogen separation coefficient α=1.
It was 88.

[Effects of the Invention] The separation membrane in which the copolymer of tetrafluoroethylene and siloxane-containing vinyl ether of the present invention is made into 1t1711 and placed on a polysulfone porous membrane is particularly effective against oxygen/
It has an excellent effect of balancing nitrogen separation coefficient and oxygen permeation rate at a high level. Furthermore, the separation membrane of the present invention is also recognized to be effective in stably maintaining this excellent performance.

Claims (1)

[Scope of Claims] 1. A gas separation membrane in which a copolymer of tetrafluoroethylene and siloxane-containing vinyl ether is made into a thin film and placed on a polysulfone porous membrane. 2. The content ratio of tetrafluoroethylene in the copolymer is 5
70 mol % of the gas separation membrane according to claim 1. 3. The gas separation membrane according to claim 1, wherein the siloxane-containing vinyl ether is a vinyloxypropyltrimethylsiloxysilane compound.